So you think you know engines eh?....

[Ryan.maccie]

Alright, So here is the sitch, Its got me at my witt's end..

Lovely young lady buys a mint s13 hatch, 106xxx km, lady driven, one owner *grandma* auto.. By far one of the minty'st cars I have seen in ages..

We take it through emissions testing, and it fails horribly in the idle portion..

Readings are as follows:
DRIVING
HC
Max:90.00
Vehicle 8.00

CO
Max: .76
Vehicle: 0.00

NOx
Max: 1117
Vehicle: 12.00

IDLE

HC
Max:108
Vehicle:276

CO:
Max: .82
Vehicle: 4.43

So, With that information I decided to look at the coolant temp sensor as the culprate, Backed that up with a satanic code 13 off the ECU.. I replaced the sensor, Code was still apparent. I than tried another brand new sensor, Code still remained.
So I checked continuity between the 3 ecu pins, and the 2 sensor pins and confirmed continuity.. Still the code was coming back. So I rewired the Blue/Orange I believe from the CTS-> pin 18(i believe), At wich point the CTS code dissappeared.. So I swapped the cat for a brand new one I had laying around along with a brand new 02 sensor.

Car failed again same readings same situation.. CTS code came back..

At this point I than played peek-aboo with code 13 for a couple days.. I have now ran the ground wire for the CTS straight to the block wich seems to have delt with that issue, For the time being..

I am now showing Code 55.

Although with code 55 being shown, the afr's measured at the tail pipe via an AEM UEGO at idle are still 12.2-13.6..

Timing is set to 15*
CTS Resistance is correct
Maf Voltage at idle is 1.44
Fuel pressure vac disconnected is ~40psi
Tps is set to .45

What am I missing that would cause the idle circut to be pig rich as it is..
I think this is something stupid and small, that I am just not thinking of..

I feel like I have tried everything at this point.. The car runs like a swiss watch, doesnt miss a beat.. But is stupid rich..

Things I think are possible at this point..

Leaky injector
Exhaust leak at manifold giving o2 sensor a false lean.

Discuss please!

[Twinkies!]

Could it be the ecu? Mine wouldn't pass smog so my neighbor gave me his bad bam! It worked

[steve shadows]

What condition is the CAT in? A lot of times they are blown out or jacked up even after 100K miles on USDM KA 240s...

[godsmack]

I'm gonna go with the leaky injector.

[Kingtal0n]

lol, air fuel is adjusted in closed-loop by the narrowband oxygen sensor. Install a narrowband oxygen sensor and let the ECU do it's job.

Or, plan B is use the analog output from the AEM to simulate a narrowband.

Either way, the ECU is capable of using that 0-1V input to modify injector pulse width.

[hooknbook240sx]

As previously mentioned I would look into the catalytic converter being bad or clogged. replace the oxygen sensor and make sure its functioning properly if that is bad its giving a false code the ecu.